## 7.4. Kernel Configuration

Darwin includes configuration directories for each major component of the operating system, as listed here:

xnu/bsd/conf
  Contains configuration files for the BSD portions of Darwin.
xnu/iokit/conf
  Contains configuration files for IOKit, Darwin's subsystem for device drivers.
xnu/libkern/conf
  Contains configuration files for libkern, a set of base classes for kernel C++ code.
xnu/libsa/conf
  Contains configuration files for implementations of standard C library functions that are used by the kernel.
xnu/osfmk/conf
  Contains configuration files for the Mach portions of Darwin.
xnu/pexpert/conf
  Contains configuration files for pexpert (platform expert). This is for low-level hardware support during the boot sequence.

libsa and pexpert are private to the xnu kernel and should not be used by kernel extensions.

To tweak machine-independent aspects of a Darwin kernel component, you can edit the MASTER file in each configuration directory. You can find machine-dependent configuration options in MASTER.i386 (for x86 systems) and MASTER.ppc (for PowerPC systems).

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